
♪ The Earth BEGAN to cool
The Big Bang Theory Season 12, Episode 4

♪ The Earth BEGAN to cool ♪
The Big Bang Theory Season 5, Episode 21

♪ The Earth BEGAN to cool
The Big Bang Theory Season 7, Episode 14

In any event, that BEGAN
a decade-long progression
The Big Bang Theory Season 7, Episode 17

♪ The Earth BEGAN to cool
The Big Bang Theory Season 12, Episode 9